Peel and stick roofing membranes with cured pressure-sensitive adhesives

ABSTRACT

A membrane composite comprising a polymeric membrane panel, an adhesive layer, and a release member, where the adhesive layer is a pressure-sensitive adhesive that is at least partially cured, and where the adhesive layer has a thickness of at least 102 μm.

This application is a U.S. National Stage Application ofPCT/US2014/056295, filed on Sep. 18, 2014, which claims the benefit ofU.S. Provisional Application Ser. No. 61/879,358, filed Sep. 18, 2013,and Ser. No. 61/983,738, filed Apr. 24, 2014, which are incorporatedherein by reference.

FIELD OF THE INVENTION

Embodiments of the invention are directed toward roofing membranes thatcarry a cured pressure-sensitive adhesive for securing the membrane to aroof surface. The pressure-sensitive adhesive is advantageously appliedto the membrane as a hot-melt adhesive and subsequently cured. A releasemember can be applied to the pressure-sensitive adhesive, therebyallowing the membrane to be rolled, delivered to a job site, andultimately applied to a roofing surface by using peel and sticktechniques.

BACKGROUND OF THE INVENTION

Large, flexible polymeric sheets, which are often referred to asmembranes or panels, are used in the construction industry to cover flator low-sloped roofs. These membranes provide protection to the roof fromthe environment, particularly in the form of a waterproof barrier. As isknown in the art, commercially popular membranes include thermosetmembranes such as those including cured EPDM (i.e.,ethylene-propylene-diene terpolymer rubber) or thermoplastics such asTPO (i.e., thermoplastic olefins).

These membranes are typically delivered to a construction site in abundled roll, transferred to the roof, and then unrolled and positioned.The sheets are then affixed to the building structure by employingvarying techniques such as mechanical fastening, ballasting, and/oradhesively adhering the membrane to the roof. The roof substrate towhich the membrane is secured may be one of a variety of materialsdepending on the installation site and structural concerns. For example,the surface may be a concrete, metal, or wood deck, it may includeinsulation or recover board, and/or it may include an existing membrane.

In addition to securing the membrane to the roof—which mode ofattachment primarily seeks to prevent wind uplift—the individualmembrane panels, together with flashing and other accessories, arepositioned and adjoined to achieve a waterproof barrier on the roof.Typically, the edges of adjoining panels are overlapped, and theseoverlapping portions are adjoined to one another through a number ofmethods depending upon the membrane materials and exterior conditions.One approach involves providing adhesives or adhesive tapes between theoverlapping portions, thereby creating a water resistant seal.

With respect to the former mode of attachment, which involves securingthe membrane to the roof, the use of adhesives allow for the formationof a fully-adhered roofing system. In other words, a majority, if notall, of the membrane panel is secured to the roof substrate, as opposedto mechanical attachment methods that can only achieve direct attachmentin those locations where a mechanical fastener actually affixes themembrane.

When adhesively securing a membrane to a roof, such as in the formationof a fully-adhered system, there are a few common methods employed. Thefirst is known as contact bonding whereby technicians coat both themembrane and the substrate with an adhesive, and then mate the membraneto the substrate while the adhesive is only partially set. Because thevolatile components (e.g. solvent) of the adhesives are flashed offprior to mating, good early (green) bond strength is developed.

Another mode of attachment is through the use of a pre-applied adhesiveto the bottom surface of the membrane. In other words, prior to deliveryof the membrane to the job site, an adhesive is applied to the bottomsurface of the membrane. In order to allow the membrane to be rolled andshipped, a release film or member is applied to the surface of theadhesive. During installation of the membrane, the release member isremoved, thereby exposing the pressure-sensitive adhesive, and themembrane can then be secured to the roofing surface without the need forthe application of additional adhesives.

As is known in the art, the pre-applied adhesive can be applied to thesurface of the membrane in the form of a hot-melt adhesive. For example,U.S. Publication No. 2004/0191508, which teaches peel and stickthermoplastic membranes, employs pressure-sensitive adhesivecompositions comprising styrene-ethylene-butylene-styrene (SEES),tackifying endblock resins such as cumarone-indene resin and tackifyingmidblock resins such as terpene resins. This publication also suggestsother hot-melt adhesives such as butyl-based adhesives, EPDM-basedadhesives, acrylic adhesives, styrene-butadiene adhesives,polyisobutylene adhesives, and ethylene vinyl acetate adhesives.

In view of the nature of the adhesives, peel and stick membranes haveinherent limitations. For example, there are temperature windows thatlimit the minimum temperature at which the membranes can be installed ona roof surface. Also, there are maximum temperature limits on the roofsurface that the adhesive can withstand while maintaining wind-upliftintegrity. With respect to the latter, where the surface temperature onthe roof nears the glass transition temperature of the adhesive, theadhesive strength offered by the pressure-sensitive adhesive is notmaintained. As a result, peel-and-stick membranes have not gained wideacceptance in the industry. Moreover, the use of peel-and-stickmembranes has been limited to use in conjunction with white membranes(e.g., white thermoplastic membranes) because the surface temperature ofthese membranes remains cooler when exposed to solar energy.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a membrane compositecomprising a polymeric membrane panel, an adhesive layer, and a releasemember, where the adhesive layer is a pressure-sensitive adhesive thatis at least partially cured, and where the adhesive layer has athickness of at least 102 μm.

Embodiments of the present invention provide a process for forming amembrane composite, the process comprising heating a melt-extrudable,UV-curable pressure-sensitive adhesive to allow the adhesive to flow,applying the adhesive to a planar surface of a membrane panel to form acoating of adhesive, subjecting the coating of the adhesive to UVradiation to thereby effect crosslinking of the adhesive, applying arelease member to the adhesive coating to form a composite, and windingthe composite.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section perspective view of a membrane compositeaccording to embodiments of the invention.

FIG. 2 is a flow chart describing a process for making membranecomposite according to embodiments of the present invention.

FIG. 3 is a schematic of a continuous process for making membranecomposite according to the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of the invention are based, at least in part, on thediscovery of roofing membranes having a pre-applied pressure-sensitiveadhesive that is at least partially cured. In one or more embodiments,the pre-applied adhesive is applied as a hot-melt adhesive andsubsequently cured. While the prior art contemplates thermoplasticmembranes that carry a pressure-sensitive adhesive applied to themembrane as a hot-melt adhesive, the hot-melt adhesives used in thepresent invention are advantageously cured, which provides the membraneswith a higher operating temperature. Further, practice of the presentinvention allows for adjustments in the formulation to achieve greatertack at lower temperatures. Still further, practice of the presentinvention is not limited to white membranes.

Membrane Construction

Practice of the present invention does not necessarily change theoverall construction of the membranes of the present invention. As theskilled person understands, membranes that carry an adhesive forapplication by peel-and-stick methods are generally known as disclosedin U.S. Publication No. 2004/0191508, which is incorporated herein byreference.

For example, a membrane 11, which may be referred to as a membranecomposite 11, is shown in FIG. 1. Membrane composite 11 includespolymeric panel 13, pressure-sensitive adhesive layer 15, and releasemember 17 removably attached to layer 15.

Membrane Panel

In one or more embodiments, the membrane may be a thermoset material. Inother embodiments the membrane may be a thermoformable material. In oneor more embodiments, the membrane may be EPDM based. In otherembodiments, the membrane may be TPO based. In these or otherembodiments, the membrane may be flexible and capable of being rolled upfor shipment. In these or other embodiments, the membrane may includefiber reinforcement, such as a scrim. In one or more embodiments, themembrane includes EPDM membranes including those that meet thespecifications of the ASTM D-4637. In other embodiments, the membraneincludes thermoplastic membranes including those that meet thespecifications of ASTM D-6878-03. Still other membranes may include PVC,TPV, CSPE, and asphalt-based membranes.

In one or more embodiments, the roofing membrane panels arecharacterized by conventional dimensions. For example, in one or moreembodiments, the membrane panels may have a thickness of from about 500am to about 3 mm, in other embodiments from about 1,000 am to about 2.5mm, and in other embodiments from about 1,500 am to about 2 mm. In theseor other embodiments, the membrane panels of the present invention arecharacterized by a width of about 1 m to about 20 m, in otherembodiments from about 2 m to about 18 m, and in other embodiments fromabout 3 m to about 15 m.

Hot-Melt Curable Adhesives

In one or more embodiments, the curable hot-melt adhesive that may beused for forming the cured pressure-sensitive adhesive layer may be anacrylic-based hot-melt adhesive. In one or more embodiments, theadhesive is a polyacrylate such as a polyacrylate elastomer. In one ormore embodiments, useful polyacrylates include one or more units definedby the formula:

where each R¹ is individually hydrogen or a hydrocarbyl group and eachR² is individually a hydrocarbyl group. In the case of a homopolymer,each R¹ and R², respectively, throughout the polymer are same in eachunit. In the case of a copolymer, at least two different R¹ and/or twodifferent R² are present in the polymer chain.

In one or more embodiments, hydrocarbyl groups include, for example,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, substituted aryl, aralkyl, alkaryl,allyl, and alkynyl groups, with each group containing in the range offrom 1 carbon atom, or the appropriate minimum number of carbon atoms toform the group, up to about 20 carbon atoms. These hydrocarbyl groupsmay contain heteroatoms including, but not limited to, nitrogen, oxygen,boron, silicon, sulfur, and phosphorus atoms. In particular embodiments,each R² is an alkyl group having at least 4 carbon atoms. In particularembodiments, R¹ is hydrogen and R² is selected from the group consistingof butyl, 2-ethylhexyl, and mixtures thereof.

In one or more embodiments, the polyacrylate elastomers that are usefulas adhesives in the practice of this invention may be characterized by aglass transition temperature (Tg) of less than 0° C., in otherembodiments less than −20° C., in other embodiments less than −30° C. Inthese or other embodiments, useful polyacrylates may be characterized bya Tg of from about −70 to about 0° C., in other embodiments from about−50 to about −10° C., and in other embodiments from about −40 to about−20° C.

In one or more embodiments, the polyacrylate elastomers that are usefulas adhesives in the practice of this invention may be characterized by anumber average molecular weight of from about 100 to about 350 kg/mole,in other embodiments from about 150 to about 270 kg/mole, and in otherembodiments from about 180 to about 250 kg/mole.

In one or more embodiments, the polyacrylate elastomers that are usefulas adhesives in the practice of this invention may be characterized by aBrookfield viscosity at 150° C. of from about 20,000 to about 70,000cps, in other embodiments from about 30,000 to about 60,000 cps, and inother embodiments from about 40,000 to about 50,000 cps.

Specific examples of polyacrylate elastomers that are useful asadhesives in the practice of the present invention includepoly(butylacrylate), and poly(2-ethylhexylacrylate). These polyacrylateelastomers may be formulated with photoinitiators, solvents,plasticizers, and resins such as natural and hydrocarbon resins. Theskilled person can readily formulate a desirable coating composition.Useful coating compositions are disclosed, for example, in U.S. Pat.Nos. 6,720,399, 6,753,079, 6,831,114, 6,881,442, and 6,887,917, whichare incorporated herein by reference.

In other embodiments, the polyacrylate elastomers may includepolymerized units that serve as photoinitiators. These units may derivefrom copolymerizable photoinitiators including acetophenone orbenzophenone derivatives. These polyacrylate elastomers and the coatingcompositions formed therefrom are known as disclosed in U.S. Pat. Nos.7,304,119 and 7,358,319, which are incorporated herein by reference.

Useful adhesive compositions are commercially available in the art. Forexample, useful adhesives include those available under the tradenameacResin (BASF), those available under the tradename AroCure (AshlandChemical), and NovaMeltRC (NovaMelt). In one or more embodiments, thesehot-melt adhesives may be cured (i.e., crosslinked) by UV light.

In one or more embodiments, the hot-melt adhesive is at least partiallycured after being applied to the membrane, as will be discussed ingreater detail below. In one or more embodiments, the adhesive is curedto an extent that it is not thermally processable in the form it wasprior to cure. In these or other embodiments, the cured adhesive ischaracterized by a cross-linked infinite polymer network. While at leastpartially cured, the adhesive layer of one or more embodiments isessentially free of curative residue such as sulfur or sulfur crosslinksand/or phenolic compounds or phenolic-residue crosslinks.

In one or more embodiments, the pressure-sensitive adhesive layer mayhave a thickness of at least 51 μm (2 mil), in other embodiments atleast 102 μm (4 mil), in other embodiments at least 127 μm (5 mil), andin other embodiments at least 152 μm (6 mil). In these or otherembodiments, the pressure-sensitive adhesive layer has a thickness of atmost 381 μm (15 mil), in other embodiments at most 305 μm (12 mil), andin other embodiments at most 254 μm (10 mil). In one or moreembodiments, the adhesive layer has a thickness of from about 51 toabout 381 μm (about 2 to about 15 mil), in other embodiments from about102 to about 305 μm (about 4 to about 12 mil), and in other embodimentsfrom about 127 to about 254 μm (about 5 to about 10 mil).

Release Member

In one or more embodiments, release member 17 may include a polymericfilm or extrudate, or in other embodiments it may include a cellulosicsubstrate. Where the polymeric film and/or cellulosic substrate cannotbe readily removed after being attached to the asphaltic component, thepolymeric film and/or cellulosic substrate can carry a coating or layerthat allows the polymeric film and/or cellulosic substrate to be readilyremoved from the asphaltic component after attachment. This polymericfilm or extrudate may include a single polymeric layer or may includetwo or more polymeric layers laminated or coextruded to one another.

Suitable materials for forming a release member that is a polymeric filmor extrudate include polypropylene, polyester, high-densitypolyethylene, medium-density polyethylene, low-density polyethylene,polystyrene or high-impact polystyrene. The coating or layer applied tothe film and/or cellulosic substrate may include a silicon-containing orfluorine-containing coating. For example, a silicone oil or polysiloxanemay be applied as a coating. In other embodiments, hydrocarbon waxes maybe applied as a coating. As the skilled person will appreciate, thecoating, which may be referred to as a release coating, can be appliedto both planar surfaces of the film and/or cellulosic substrate. Inother embodiments, the release coating need only be applied to theplanar surface of the film and/or cellulosic substrate that isultimately removably mated with the asphaltic component.

In one or more embodiments, the release member is characterized by athickness of from about 15 to about 80, in other embodiments from about18 to about 75, and in other embodiments from about 20 to about 50 μm.

Preparation of Membrane Composite

The membrane panels employed in the membrane composites of the presentinvention may be prepared by conventional techniques. For example,thermoplastic membrane panels may be formed by the extrusion ofthermoplastic compositions into one or more layers that can be laminatedinto a membrane panel. Thermoset membranes can be formed using knowncalendering and curing techniques. Alternatively, thermoset membranescan be made by continuous process such as those disclosed in WO2013/142562, which is incorporated herein by reference. Once themembrane is formed, the curable hot-melt adhesive can be extruded ontothe membrane by using known apparatus such as adhesive coaters. Theadhesive can then subsequently be cured by using, for example, UVradiation. The release film can be applied to the adhesive layer, andthe membrane can then be subsequently rolled for storage and/orshipment. Advantageously, where the membrane panel is made by usingcontinuous techniques, the process can be supplemented with continuoustechniques for applying and curing the adhesive coatings according toembodiments of the present invention to thereby prepare usable membranecomposites within a single continuous process.

As generally shown in FIG. 2, process 30 for preparing a compositemembrane according to the present invention generally begins with a stepof heating 32, wherein a pressure-sensitive adhesive is heated to asufficient temperature to allow the adhesive to be applied as a coatingwithin a coating step 34. Within coating step 34, the adhesive isapplied to the membrane to form a coating layer. Following formation ofthe coating, the coating is subjected to a UV-curing step 36 wheresufficient UV energy is applied to the coating to thereby effect adesirable curing or crosslinking of the adhesive. Once the adhesive hasbeen sufficiently cured by exposure to UV curing step 36, a releasemember can be applied to the cured coating in a member application step38. Following application of a member, the composite is wound into aroll at winding step 40.

In one or more embodiments, heating step 32 heats the adhesive to atemperature of from about 120 to about 160° C., in other embodimentsfrom about 125 to about 155° C., and in other embodiments from about 130to about 150° C.

In one or more embodiments, coating step 34 applies an adhesive to thesurface of a membrane to form a coating layer of adhesive that has athickness of at least 51 μm (2 mil), in other embodiments at least 102μm (4 mil), in other embodiments at least 127 μm (5 mil), and in otherembodiments at least 152 μm (6 mil). In one or more embodiments, coatingstep 34 applies an adhesive to the surface of a membrane to form acoating layer of adhesive that has a thickness of from about 51 to about381 μm (about 2 to about 15 mil), in other embodiments from about 102 toabout 305 μm (about 4 to about 12 mil), and in other embodiments fromabout 127 to about 254 μm (about 5 to about 10 mil). In one or moreembodiments, the coating has a uniform thickness such that the thicknessof the coating at any given point on the surface of the membrane doesnot vary by more than 51 μm (2 mil), in other embodiments by more than38 μm (1.5 mil), and in other embodiments by more than 25 μm (1 mil).

In one or more embodiments, UV curing step 36 subjects the adhesivecoating to a UV dosage of from about 30 to about 380 millijoule/cm², inother embodiments from about 35 to about 300 millijoule/cm², in otherembodiments from about 40 to about 280 millijoule/cm², in otherembodiments from about 45 to about 240 millijoule/cm², and in otherembodiments from about 48 to about 235 millijoule/cm². It hasadvantageously been discovered that the required dosage of energy can beexceeded without having a deleterious impact on the adhesives of thepresent invention. For example, up to ten times, in other embodiments upto five times, and in other embodiments up to three times the requireddosage can be applied to the coating composition without having adeleterious impact on the coating composition and/or its use in thepresent invention.

In one or more embodiments, UV curing step 36 subjects the adhesivecoating to a UV intensity, which may also be referred to as UVirradiance, of at least 150, in other embodiments at least 200, and inother embodiments at least 250 milliWatts/cm². In these or otherembodiments, UV curing step 36 subjects the adhesive coating to a UVintensity of from about 150 to about 500 milliWatts/cm², in otherembodiments from about 200 to about 400 milliWatts/cm², and in otherembodiments from about 250 to about 350 milliWatts/cm². It hasadvantageously been discovered that the ability to appropriately curethe coating compositions of the present invention, and thereby provide auseful pressure-sensitive adhesive for the roofing applicationsdisclosed herein, critically relies on the UV intensity applied to thecoating. It is believed that the thickness of the coatings (andtherefore the thickness of the pressure-sensitive adhesive layer)employed in the present invention necessitates the application ofgreater UV intensity.

In one or more embodiments, the energy supplied to the coating layerwithin UV radiation step 36 is in the form of UV-C electromagneticradiation, which can be characterized by a wave length of from about 250to about 260 nm. In one or more embodiments, the UV dosage appliedduring UV curing step 36 is regulated based upon a UV measuring andcontrol system that operates in conjunction with UV curing step 36.According to this system, UV measurements are taken proximate to thesurface of the adhesive coating layer using known equipment such as a UVradiometer. The data from these measurements can be automaticallyinputted into a central processing system that can process theinformation relative to desired dosage and/or cure states andautomatically send signal to various variable-control systems that canmanipulate one or more process parameters. For example, the powersupplied to the UV lamps and/or the height at which the UV lamps arepositioned above the coating layer can be manipulated automaticallybased upon electronic signal from the central processing unit. In otherwords, the UV intensity, and therefore the UV dosage, can be adjusted inreal time during the manufacturing process.

In one or more embodiments, an exemplary process for preparing themembrane composites of the present invention can be described withreference to FIG. 3. Continuous process 50 includes a heating step 52where UV curable hot-melt adhesive 51 is heated to a desired temperaturewithin a heated tank 53. Adhesive 51 is fed into an extrusion device,such as a coater 55, which may include a pump, such as a gear pump 57,and a slot die 59. Within coating step 54, coater 55 extrudes adhesive51, which is in its molten, liquid or flowable state, and deposits acoating layer 61 of adhesive 51 onto a planar surface 63 of membrane 65.

As shown in FIG. 3, coating step 54 can include a roll-coatingoperation, where adhesive 51 is applied to membrane 65 while membrane 65is at least partially wound around a coating mandrel 67. Membrane 65carrying coating layer 61 is fed to a crosslinking step 56, wherecoating layer 61 of adhesive 51 is subjected to a desired dosage of UVradiation 69, which may be supplied by one or more UV lamps 71. UV lamps71 may include, for example, mercury-type UV lamps or LED UV lamps. Asthe skilled person appreciates, the desired dosage of UV energy can besupplied to coating 61 by adjusting the UV intensity and exposure time.The intensity can be manipulated by the power supplied to the respectivelamps and the height (H) that the lamps are placed above the surface ofcoating 61 of adhesive 51. Exposure time can be manipulated based uponthe line speed (i.e., the speed at which membrane 65 carrying coatinglayer 61 is passed through UV curing step 56).

Following UV curing step 56, release paper 73 may be applied to uppersurface 75 of coating layer 61 within release paper application step 58.As shown in FIG. 3, release paper 73 may be supplied from a mandrel 77and removably mated to upper surface 75 through pressure supplied by niprolls 79. After application of release paper 73, the composite productmay be wound within winding step 60 to provide wound rolls 81 ofcomposite products 83.

Characteristics of Composite Membrane

In one or more embodiments, the layer of crosslinked pressure-sensitiveadhesive disposed on a surface of the membrane according to the presentinvention may be characterized by an advantageous peel strength. In oneor more embodiments, the peel strength of the layer of crosslinkedpressure-sensitive adhesive disposed on the membranes of the presentinvention may be characterized by a peel strength, as determinedaccording to Pressure Sensitive Tape Council (PSTC) 101, of at least3.0, in other embodiments at least 3.5, and in other embodiments atleast 4.0. In these or other embodiments, the peel strength may be fromabout 3.0 to about 25 in other embodiments from about 3.5 to about 20,and in other embodiments from about 4.0 to about 18 psi.

In one or more embodiments, the layer of crosslinked pressure-sensitiveadhesive disposed on a surface of the membrane according to the presentinvention may be characterized by an advantageous dead load shear. Inone or more embodiments, the dead load shear of the layer of crosslinkedpressure-sensitive adhesive disposed on the membranes of the presentinvention may be characterized by a dead load shear, as determinedaccording to PSTC 107, of at least 0.5 hour (time of failure), in otherembodiments at least 1.0 hour, and in other embodiments at least 1.5. Inthese or other embodiments, the dead load shear may be from about 2.0 toabout 2.5 hours.

Application to a Roof Surface

The membrane composites of the present invention can advantageously beapplied to a roof surface (also known as roof substrate) by usingstandard peel and stick techniques. For example, the membrane can beunrolled on a roof surface and placed into position. Portions of themembrane are then typically folded back and portions of the releasemember are removed. The membrane can then subsequently be adhered to theroof surface by using various techniques including the use of rollersand the like to mate the adhesive to the substrate. Where multiplemembrane panels are employed, the seams can be secured by usingconventional techniques. For example, thermoplastic membranes can bewielded together at the seam. Where thermoset membranes are employed,either liquid adhesives or tapes can be used to form a seam. It hasadvantageously been discovered that the pressure-sensitive adhesivelayer employed in the membranes of the present invention allows themembranes to be adhered to a variety of roofing surfaces. These include,but are not limited to, wood decks, concrete decks, steel decks, facedconstruction boards, and existing membrane surfaces. In particularembodiments, the membranes of the present invention are adhered, throughthe cured adhesive layer disclosed herein, to a faced construction boardsuch as, but not limited to, polyisocyanurate insulation boards or coverboards that include facers prepared from polar materials. For example,the adhesives of the present invention provide advantageous adhesion tofacers that contain cellulosic materials and/or glass materials. It isbelieved that the polar nature of the adhesive is highly compatible withthe polar nature of these facer materials and/or any adhesives orcoatings that may be carried by glass or paper facers. Accordingly,embodiments of the present invention are directed toward a roof deckincluding a construction board having a cellulosic or glass facer and amembrane secured to the construction board through an at least partiallycured polyacrylate adhesive layer in contact with a glass or cellulosicfacer of the construction board.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES

In order to demonstrate the practice of the present invention, a 60 mil(1.5 mm) EPDM membrane was coated with a UV-curable, melt-extrudablepolyacrylate adhesive (ac Resin A-250 UV™ from BASF), and wassubsequently cured by UV radiation. The membrane was then secured to astainless steel panel, and the test specimen was then subjected to peelstrength testing according to PSTC 101 and dead load shear testingaccording to PSTC 107. The table below provides the coating thickness,the UV intensity applied to the sample, the UV dose applied to thesample, and the results of the peel and shear testing.

Samples 1 2 3 Adhesive Thickness (mil) 6.0 6.0 6.0 UV Intensity (mW/cm²)105 276 276 UV Dose (mJ/cm²) 60 60 235 Peel Strenght (pli) 159.1 111.787.5 Shear (Hr) 0.5 10.0 9.1

The data not only demonstrates the usefulness of the present invention,but also highlights the advantages associated with curing the adhesivewith higher UV intensity. Also, the data shows that increased dosages ofUV energy can be applied without deleteriously impacting the adhesive.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. A process for forming a roofing membranecomposite, the process comprising: (a) heating a melt-extrudable,UV-curable pressure-sensitive adhesive to allow the adhesive to flow,where the adhesive consists of a polyacrylate elastomer and, optionally,one or more of photoinitiators, solvents, plasticizers, and resinsselected from the group consisting of natural resins and hydrocarbonresins; (b) applying the adhesive to a planar surface of a thermoplasticor cured rubber roofing membrane panel for providing a weatherproofpolymeric barrier to a building structure, to thereby form a coatinglayer of adhesive having a thickness of at least 152 μm, where theroofing membrane panel has a thickness of from about 500 μm to about 3mm; (c) subjecting the coating layer of the adhesive to UV radiation tothereby effect crosslinking of the adhesive to form a cross-linkedinfinite polymer network; (d) applying a release member to the adhesivecoating layer to form a roofing member composite; and (e) winding thecomposite.
 2. The process of claim 1, where said step of heating heatsthe adhesive to a temperature of from about 120 to about 160° C.
 3. Theprocess of claim 1, where said step of subjecting the coating to UVradiation includes subjecting the adhesive to a UV dosage of from about50 to about 230 millijoules/cm².
 4. The process of claim 1, where saidstep of subjecting the coating to UV radiation includes subjecting theadhesive to at least 150 milliWatts/cm² of UV energy.
 5. The process ofclaim 1, where said step of subjecting the coating to UV radiationincludes subjecting the adhesive to at least 200 milliWatts/cm² of UVenergy.
 6. The process of claim 1, where the adhesive includes one ormore units deriving from butyl acrylate or 2-ethylhexyl acrylate.
 7. Theprocess of claim 1, where the adhesive has a Tg of less than 0° C. 8.The process of claim 1, where the roofing membrane panel has a width offrom about 1 to about 20 meters.